1. Field of the Invention
This invention relates to a dobby used in weaving by a weaving machine, and more particularly, to a dobby for electromagnetically controlling a heald frame to be moved upwards or downwards.
2. Description of the Prior Art
A dobby for electromagnetically controlling a heald frame to be moved upwards or downwards generally comprises a plurality of working mechanisms each including a vertical lever connected to the heald frame: a pair of connection hooks pivotally attached to the vertical lever; a pair of knife hooks periodically moved reversely to each other in the direction of approaching and leaving the connection hooks; a pair of rockable command levers for controlling the knife hooks to selectively displace to a first position where the knife hooks cannot be engaged with the connection hooks and to a second position where the knife hooks can be engaged with the connection hooks; a rockable pusher for controlling the position of the command lever; a rockable selection lever for displacing the command lever so as to selectively displace the knife hooks to the first and second positions; and an electromagnet for releasably holding the selection lever so as to selectively displace the knife hooks to the first and second positions (Japanese Pat. Publication Nos. 2-23611 and 3-4658).
In a dobby known per se, one or more heald frames are connected to the vertical lever in each working mechanism through a link mechanism or the like. When the selection lever is not held on the magnet, the pusher is maintained at the position where the pusher is out of contact with the command lever so that the knife hooks are maintained at the first position where the knife hooks cannot be engaged with the connection hooks. On the other hand, when the selection lever is held on the magnet, the pusher is maintained at the position where the pusher can be in contact with the command lever and under this condition the pusher is rocked to push the command lever so that the knife hooks are maintained at the second position where the knife hooks can be engaged with the connection hooks.
Since the vertical lever is not moved even though the knife hooks are moved while they are not engaged with the connection hooks, one or more heald frames connected to the vertical lever are not moved. However, if the knife hooks are moved while they are engaged with the connection hooks, the vertical lever is moved in one direction, so that one or more heald frames connected to the vertical lever are moved.
In the dobby known per se, however, the pusher is usually made apart from the command lever. Therefore, when the knife hooks are engaged with the connection hooks, the pusher is moved in the vertical direction with the selection lever held on the magnet, so that the pusher collides with the command lever. Therefore, in the dobby known per se, the impact when the pusher collides with the command lever is large and in some cases, the selection lever held on the magnet is separated from the magnet.
Particularly, in the dobby provided with a spring which allows a force for separating the selection lever from the magnet to be applied to the selection lever, the selection lever is often separated from the magnet by the impact when the pusher collides with the command lever. In this manner, when the selection lever held on the magnet is separated from the magnet, the knife hooks are not correctly engaged with the connection hooks and therefore, the heald frame is not correctly moved, resulting in mis-weaving.